Review article
Technology Advances to Improve Response to Cardiac Resynchronization Therapy: What Clinicians Should KnowAvances tecnológicos para mejorar la respuesta ventricular en la resincronización cardiaca: lo que el clínico debe conocer

https://doi.org/10.1016/j.rec.2018.01.006Get rights and content

Abstract

Cardiac resynchronization therapy (CRT) is a well-established treatment for symptomatic heart failure patients with reduced left ventricular ejection fraction, prolonged QRS duration, and abnormal QRS morphology. The ultimate goals of modern CRT are to improve the proportion of patients responding to CRT and to maximize the response to CRT in patients who do respond. While the rate of CRT nonresponders has moderately but progressively decreased over the last 20 years, mostly in patients with left bundle branch block, in patients without left bundle branch block the response rate is almost unchanged. A number of technological advances have already contributed to achieve some of the objectives of modern CRT. They include novel lead design (the left ventricular quadripolar lead, and multipoint pacing), or the possibility to go beyond conventional delivery of CRT (left ventricular endocardial pacing, His bundle pacing). Furthermore, to improve CRT response, a triad of actions is paramount: reducing the burden of atrial fibrillation, reducing the number of appropriate and inappropriate interventions, and adequately predicting heart failure episodes. As in other fields of cardiology, technology and innovations for CRT delivery have been at the forefront in transforming–improving–patient care; therefore, these innovations are discussed in this review.

Resumen

La terapia de resincronización cardiaca (TRC) es un tratamiento establecido para los pacientes con insuficiencia cardiaca, fracción de eyección reducida y con intervalo QRS ancho El objetivo actual de la TRC es «incrementar la tasa de pacientes respondedores a la resincronización». Si bien la tasa de no respondedores a la TRC ha ido decreciendo en los últimos 20 años, sobre todo en los pacientes con bloqueo de rama izquierda, en aquellos pacientes sin bloqueo de rama izquierda dicha tasa se ha mantenido inalterada. Ciertos avances tecnológicos recientes han contribuido a aumentar la tasa de respondedores a la TRC. Entre ellos los nuevos diseños de los cables (cable cuadripolar de ventrículo izquierdo con estimulación en varios puntos), o la posibilidad de ir más allá de la TRC convencional (estimulación endocárdica en ventrículo izquierdo, estimulación del haz de His). Además, para mejorar la tasa de respondedores, se tienen que abordar 3 aspectos: reducir la carga de fibrilación auricular, reducir el número de intervenciones apropiadas e inapropiadas y predecir con precisión los episodios de insuficiencia cardiaca. En esta revisión se presentan las últimas innovaciones tecnológicas en la TRC, las cuales prentenden transformar (mejorar), como en otras áreas de la cardiología, el manejo y cuidado de los pacientes.

Section snippets

INTRODUCTION

Cardiac resynchronization therapy (CRT) is a well-established nonpharmacological treatment for symptomatic heart failure (HF) patients with reduced left ventricular ejection fraction (LVEF), prolonged QRS duration, and abnormal QRS morphology. As recently reported by the ALTITUDE registry,1 the improved outcome of CRT patients observed over the last decade is related to greater adherence to pharmacological therapy and device therapy as recommended by clinical practice guidelines.2, 3 According

IMPORTANCE OF THE LV QUADRIPOLAR LEAD, AND LV MULTIPOINT PACING

Several studies have confirmed the importance of targeting a late activated electrical/mechanical area of the left ventricle for LV pacing.5, 6 The design, shape and characteristics of LV pacing leads have considerably evolved during the past decades, driven by the clinical need to match a wide variety of cardiac vein anatomies while ensuring high mechanical stability and electrical performance. Left ventricular leads evolved from a single-electrode lead to the current quadripolar-electrode

BEYOND CONVENTIONAL DELIVERY OF CRT

In the most recent years, a number of physiological considerations have challenged the concept of traditional delivery of CRT. The first of these concepts–LV endocardial pacing–is based on the observation that conventional CRT is delivered by placing a pacing lead at the endocardium of the right ventricle and one lead on the epicardial LV wall. This pacing configuration thus reverses the physiological LV activation (ie, from endocardium to epicardium).18, 19 The second concept–His bundle

HOW CAN WE IMPROVE THE RESPONSE TO CRT?

Among several factors that could adversely affect the response to CRT, suboptimal optimization of the AV delay and VV timing of the CRT device represents the most common–and supposedly the most readily correctable–variable.27 Several studies have demonstrated the acute hemodynamic benefits of optimization of AV and VV timings.28 Although echocardiography-guided optimization is an easily accessible method, it nevertheless remains a logistical challenging and resource-intensive process, with the

THE BURDEN OF ATRIAL FIBRILLATION

Although AF occurs in more than 25% of eligible CRT patients, the available evidence of benefit from CRT in patients with any type of AF is limited to observational trials or to registry data. The prognosis of HF patients with AF is generally worse than that of patients in sinus rhythm,34 and therapy with beta-blocking agents–although effectively reducing heart rate–does not impact on mortality.35

The use of CRT in HF patients who are either at risk of developing AF or already have a history of

SHOCK-REDUCING STRATEGIES IN PATIENTS WITH CRT WITH DEFIBRILLATION

The occurrence of both appropriate and inappropriate implantable cardioverter-defibrillator (ICD) shock is associated with a subsequent 3- to 5-fold increased risk of death among patients with primary prevention ICDs.45 Interventions aiming to reduce the number of shocks consist of the administration of antiarrhythmic drugs, device-programmed arrhythmia terminating algorithms, and ablation strategies. Data from the MADIT-CRT trial (Multicenter Automatic Defibrillator Implantation with CRT)

THE PREDICTION OF EPISODES OF HEART FAILURE

The prediction of episodes of HF decompensation is an important goal from a patient's, physician's and health care economics perspective. Most of the risk scores used so far to identify patients at risk for the development of HF or mortality, assess a static risk at baseline or in an in-hospital setting. In contrast, implantable medical devices such as pacemakers, ICDs, and CRTs can provide daily measurements of multiple “diagnostic” parameters for possible evaluation of patients’ clinical

CONCLUSIONS AND FUTURE PROSPECTS

The recognition by Carl Wiggers more than 90 years ago that conduction disturbances lead to LV dysfunction54 can be traced to experiments that provided the paradigm for CRT.55 Pacemaker technology, designed to correct ventricular conduction disturbances, was eventually tested in randomized, controlled CRT trials, driven by engineers, clinicians, and the industry. As probably in other fields of cardiology, technology and innovations for CRT delivery have been at the forefront in

CONFLICTS OF INTEREST

A. Auricchio is a consultant to Medtronic, Boston Scientific, Biosense Webster, and LivaNova and has received speaker's fees from Medtronic, Boston Scientific, and LivaNova.

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